Aluminum has a high energy density (83.8 MJ/L) relative to other metals and has more than twice the energy density of gasoline (38 MJ/L). Aluminum is also highly reactive with oxidizing agents, making it a useful source of hydrogen. For example, when aluminum is brought into contact with water, hydrogen is generated through the following reaction:2Al+6H2O2Al(OH)3+3H2+Heat  [Eq. 1]Thus, aluminum has the potential to be a safe source of hydrogen. Under normal environmental conditions, however, a protective oxide coating forms on aluminum. This oxide coating forms rapidly and is stable, creating an obstacle to the production of useful amounts of hydrogen and heat from the exposure of aluminum to water.